In the scene where the team jumps into the first level of Robert Fischer Jr.'s (Cillian Murphy) dream, a firefight erupts outside their hideout in an abandoned garage. When it comes time to throw down some lead, Arthur shoulders his Mk-16 SCAR and lets 'er rip.

It took me a few rewinds to make sure it was a 16 rather than a 17, but sure enough, it's a 16. You can't buy this kind of publicity...or maybe you can?